Low Testosterone Is in the Genes

A man's risk of low testosterone is influenced by his genes, a new study says.

The study, which examined the genomes of more than 14,00 men, found changes within a single gene that were associated with low levels of testosterone in the blood.

The researchers call these changes "risk markers." Men with three or more of these risk markers were 6.5 times more likely to have low testosterone compared with men with no risk markers.

The effect of these genetic markers on testosterone levels is substantial, and on par with the effect of known risk factors for low testosterone, including age, smoking and body weight, the researchers said.

Only about 1.5 percent of the men in the study had three or more of these risk markers, said study researcher Claes Ohlsson, of the University of Gothenburg in Sweden.

These markers may assist doctors in identifying men who have a higher chance of developing low testosterone, the researchers said. For men, low levels of the sex hormone are linked with a slew of health problems, including an increased risk of Type 2 diabetes, osteoporosis, atherosclerosis and dying from heart disease.

In the new study, the researchers identified the markers by analyzing the genomes of about 8,900 men, and confirmed the link in three groups of 5,500 people total.

Most of the risk markers were found within a single gene, called the sex hormone-binding globulin gene. This gene codes for a protein that binds to testosterone. An increase in the levels of this protein might lead to a decrease in the amount of testosterone in the blood, Ohlsson said.

Genetic markers associated with low testosterone levels were also found on the X chromosome. Future studies will probably yield additional markers, the researchers said.

The researchers said they next want to examine the effect of these markers on other hormone disorders, including male infertility.

Pass it on: New genetic markers for low testosterone in men have been found.